The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: cyclobutch on 03.03. 2014 09:58

Title: Loose Sprocket
Post by: cyclobutch on 03.03. 2014 09:58
Rolling my Bitza in and out of the garage at the weekend - it's the only mileage it's been doing since around October time; I noticed a dragging noise off the back some where. Investigation revealed the chain rubbing at the front of the rear mudguard ... intermittently. Further investigation showed the rear sprocket holding bolts to be loose. I have a QD wheel fitted.

Eek, and out with the spanners. BSW/BSF, no decent fit. AF same. Metric? No, but this is the nearest. What spanners should I require for these bolt heads? 
Title: Re: Loose Sprocket
Post by: duTch on 03.03. 2014 11:11

 Do you mean a chainwheel with a replaceable sprocket band, with about 10 or 12 short  bolts?
   Sounds like a A65/50 one, I have one with socket cap screws so can't help with spanner size-  could be UNF threads from memory, bsf at a stretch, have you measured them across flats....? possibly factory specials
Title: Re: Loose Sprocket
Post by: cyclobutch on 03.03. 2014 12:39
Nah. Its a dished type sprocket - not stamped out; forged maybe? Just four retaining bolts. Measuring up I'm getting somewhere around 13.65 - 13.80 mm AF. Switching that to an imperial AF size would somewhere around 17/32" (13.49) to 35/64" (13.89 mm). I'm unsure what the AF sizes actually are on BSF/BSW spanners?

I just about got enough grip with a 14mm, but it clearly ain't right. 
Title: Re: Loose Sprocket
Post by: duTch on 03.03. 2014 13:06

1/4 ww is smaller, I'd say most likely then, but that sprocket is not in my league, sorry
Title: Re: Loose Sprocket
Post by: trevinoz on 03.03. 2014 21:52
I think that a 5/16" BS hex is 0.520" which sounds awfully close to what you have.

Trev.